SLFN5-mediated chromatin dynamics sculpt higher-order DNA repair topology.

Repair of DNA double-strand breaks (DSBs) elicits three-dimensional (3D) chromatin topological changes. A recent finding reveals that 53BP1 assembles into a 3D chromatin topology pattern around DSBs. How this formation of a higher-order structure is configured and regulated remains enigmatic. Here, we report that SLFN5 is a critical factor for 53BP1 topological arrangement at DSBs. Using super-resolution imaging, we find that SLFN5 binds to 53BP1 chromatin domains to assemble a higher-order microdomain architecture by driving damaged chromatin dynamics at both DSBs and deprotected telomeres. Mechanistically, we propose that 53BP1 topology is shaped by two processes: (1) chromatin mobility driven by the SLFN5-LINC-microtubule axis and (2) the assembly of 53BP1 oligomers mediated by SLFN5. In mammals, SLFN5 deficiency disrupts the DSB repair topology and impairs non-homologous end joining, telomere fusions, class switch recombination, and sensitivity to poly (ADP-ribose) polymerase inhibitor. We establish a molecular mechanism that shapes higher-order chromatin topologies to safeguard genomic stability.

Tandem Deubiquitination and Acetylation of SPRTN Promotes DNA-Protein Crosslink Repair and Protects against Aging.

DNA-protein crosslinks (DPCs) are highly toxic DNA lesions that threaten genomic integrity. Recent findings highlight that SPRTN, a specialized DNA-dependent metalloprotease, is a central player in proteolytic cleavage of DPCs. Previous studies suggest that SPRTN deubiquitination is important for its chromatin association and activation. However, the regulation and consequences of SPRTN deubiquitination remain unclear. Here we report that, in response to DPC induction, the deubiquitinase VCPIP1/VCIP135 is phosphorylated and activated by ATM/ATR. VCPIP1, in turn, deubiquitinates SPRTN and promotes its chromatin relocalization. Deubiquitination of SPRTN is required for its subsequent acetylation, which promotes SPRTN relocation to the site of chromatin damage. Furthermore, Vcpip1 knockout mice are prone to genomic instability and premature aging. We propose a model where two sequential post-translational modifications (PTMs) regulate SPRTN chromatin accessibility to repair DPCs and maintain genomic stability and a healthy lifespan.

A small protein encoded by PCBP1-AS1 is identified as a key regulator of influenza virus replication via enhancing autophagy.

Many annotated long noncoding RNAs (lncRNAs) contain small open reading frames (sORFs), some of which have been demonstrated to encode small proteins or micropeptides with fundamental biological importance. However, functions of lncRNAs-encoded small proteins or micropeptides in viral pathogenesis remain largely unexplored. Here, we identified a 110-amino acid small protein as a key regulator of influenza A virus (IAV) replication. This small protein that we call PESP was encoded by the putative lncRNA PCBP1-AS1. It was observed that both PCBP1-AS1 and PESP were significantly upregulated by IAV infection. Furthermore, they were markedly induced by treatment with either type I or type III interferon. Overexpression of either PCBP1-AS1 or PESP alone significantly enhanced IAV replication. In contrast, shRNA-mediated knockdown of PCBP1-AS1 or CRISPR/Cas9-mediated knockout of PESP markedly inhibited the viral production. Moreover, the targeted deletion or mutation of the sORF within the PCBP1-AS1 transcript, which resulted in the disruption of PESP expression, significantly diminished the capacity of PCBP1-AS1 to enhance IAV replication, underscoring the indispensable role of PESP in the facilitation of IAV replication by PCBP1-AS1. Interestingly, overexpression of PESP enhanced the IAV-induced autophagy by increasing the expression of ATG7, an essential autophagy effector enzyme. We also found that the 7-22 amino acids at the N-terminus of PESP were crucial for its functionality in modulating ATG7 expression and action as an enhancer of IAV replication. Additionally, HSP90AA1, a protein identified previously as a facilitator of autophagy, was found to interact with PESP, resulting in the stabilization of PESP and consequently an increase in the production of IAV. These data reveal a critical lncRNA-encoded small protein that is induced and exploited by IAV during its infection, and provide a significant insight into IAV-host interaction network.

ATG7/GAPLINC/IRF3 axis plays a critical role in regulating pathogenesis of influenza A virus.

Autophagy-related protein 7 (ATG7) is an essential autophagy effector enzyme. Although it is well known that autophagy plays crucial roles in the infections with various viruses including influenza A virus (IAV), function and underlying mechanism of ATG7 in infection and pathogenesis of IAV remain poorly understood. Here, in vitro studies showed that ATG7 had profound effects on replication of IAV. Depletion of ATG7 markedly attenuated the replication of IAV, whereas overexpression of ATG7 facilitated the viral replication. ATG7 conditional knockout mice were further employed and exhibited significantly resistant to viral infections, as evidenced by a lower degree of tissue injury, slower body weight loss, and better survival, than the wild type animals challenged with either IAV (RNA virus) or pseudorabies virus (DNA virus). Interestingly, we found that ATG7 promoted the replication of IAV in autophagy-dependent and -independent manners, as inhibition of autophagy failed to completely block the upregulation of IAV replication by ATG7. To determine the autophagy-independent mechanism, transcriptome analysis was utilized and demonstrated that ATG7 restrained the production of interferons (IFNs). Loss of ATG7 obviously enhanced the expression of type I and III IFNs in ATG7-depleted cells and mice, whereas overexpression of ATG7 impaired the interferon response to IAV infection. Consistently, our experiments demonstrated that ATG7 significantly suppressed IRF3 activation during the IAV infection. Furthermore, we identified long noncoding RNA (lncRNA) GAPLINC as a critical regulator involved in the promotion of IAV replication by ATG7. Importantly, both inactivation of IRF3 and inhibition of IFN response caused by ATG7 were mediated through control over GAPLINC expression, suggesting that GAPLINC contributes to the suppression of antiviral immunity by ATG7. Together, these results uncover an autophagy-independent mechanism by which ATG7 suppresses host innate immunity and establish a critical role for ATG7/GAPLINC/IRF3 axis in regulating IAV infection and pathogenesis.

Syk Facilitates Influenza A Virus Replication by Restraining Innate Immunity at the Late Stage of Viral Infection.

Spleen tyrosine kinase (Syk) has recently come forth as a critical regulator of innate immune response. Previous studies identify Syk as a key kinase for STAT1 activation at the early stage of influenza A virus (IAV) infection that is involved in initial antiviral immunity. However, the involvement of Syk in host antiviral immunity during the late phase of IAV infection and its effect on pathogenesis of the virus remain unknown. Here, we found through time course studies that Syk restrained antiviral immune response at the late stage of IAV infection, thereby promoting viral replication. Depletion of Syk suppressed IAV replication in vitro, whereas ectopic expression of Syk facilitated viral replication. Moreover, Syk-deficient mice were employed, and we observed that knockout of Syk rendered mice more resistant to IAV infection, as evidenced by a lower degree of lung injury, slower body weight loss, and an increased survival rate of Syk knockout mice challenged with IAV. Furthermore, we revealed that Syk repressed the interferon response at the late stage of viral infection. Loss of Syk potentiated the expression of type I and III interferons in both Syk-depleted cells and mice. Mechanistically, Syk interacted with TBK1 and modulated its phosphorylation status, thereby impeding TBK1 activation and restraining innate immune signaling that governs interferon response. Together, these findings unveil a role of Syk in temporally regulating host antiviral immunity and advance our understanding of complicated mechanisms underlying regulation of innate immunity against viral invasion. IMPORTANCE Innate immunity must be tightly controlled to eliminate invading pathogens while avoiding autoimmune or inflammatory diseases. Syk is essential for STAT1 activation at the early stage of IAV infection, which is critical for initial antiviral responses. Surprisingly, here a time course study showed that Syk suppressed innate immunity during late phases of IAV infection and thereby promoted IAV replication. Syk deficiency enhanced the expression of type I and III interferons, inhibited IAV replication, and rendered mice more resistant to IAV infection. Syk impaired innate immune signaling through impeding TBK1 activation. These data reveal that Syk participates in the initiation of antiviral defense against IAV infection and simultaneously contributes to the restriction of innate immunity at the late stage of viral infection, suggesting that Syk serves a dual function in regulating antiviral responses. This finding provides new insights into complicated mechanisms underlying interaction between virus and host immune system.

DOCK7 protects against replication stress by promoting RPA stability on chromatin.

RPA is a critical factor for DNA replication and replication stress response. Surprisingly, we found that chromatin RPA stability is tightly regulated. We report that the GDP/GTP exchange factor DOCK7 acts as a critical replication stress regulator to promote RPA stability on chromatin. DOCK7 is phosphorylated by ATR and then recruited by MDC1 to the chromatin and replication fork during replication stress. DOCK7-mediated Rac1/Cdc42 activation leads to the activation of PAK1, which subsequently phosphorylates RPA1 at S135 and T180 to stabilize chromatin-loaded RPA1 and ensure proper replication stress response. Moreover, DOCK7 is overexpressed in ovarian cancer and depleting DOCK7 sensitizes cancer cells to camptothecin. Taken together, our results highlight a novel role for DOCK7 in regulation of the replication stress response and highlight potential therapeutic targets to overcome chemoresistance in cancer.

A novel imatinib-upregulated long noncoding RNA plays a critical role in inhibition of tumor growth induced by Abl oncogenes.

BACKGROUND: Dysregulation of long noncoding RNAs (lncRNAs) has been linked to various human cancers. Bcr-Abl oncogene that results from a reciprocal translocation between human chromosome 9 and 22, is associated with several hematological malignancies. However, the role of lncRNAs in Bcr-Abl-induced leukemia remains largely unexplored. METHODS: LncRNA cDNA microarray was employed to identify key lncRNAs involved in Bcr-Abl-mediated cellular transformation. Abl-transformed cell survival and xenografted tumor growth in mice were evaluated to dissect the role of imatinib-upregulated lncRNA 1 (IUR1) in Abl-induced tumorigenesis. Primary bone marrow transformation and in vivo leukemia transplant using lncRNA-IUR1 knockout (KO) mice were further conducted to address the functional relevance of lncRNA-IUR1 in Abl-mediated leukemia. Transcriptome RNA-seq and Western blotting were performed to determine the mechanisms by which lncRNA-IUR1 regulates Bcr-Abl-induced tumorigenesis. RESULTS: We identified lncRNA-IUR1 as a critical negative regulator of Bcr-Abl-induced tumorigenesis. LncRNA-IUR1 expressed in a very low level in Bcr-Abl-positive cells from chronic myeloid leukemia patients. Interestingly, it was significantly induced in Abl-positive leukemic cells treated by imatinib. Depletion of lncRNA-IUR1 promoted survival of Abl-transformed human leukemic cells in experiments in vitro and xenografted tumor growth in mice, whereas ectopic expression of lncRNA-IUR1 sensitized the cells to apoptosis and suppressed tumor growth. In concert, silencing murine lncRNA-IUR1 in Abl-transformed cells accelerated cell survival and the development of leukemia in mice. Furthermore, lncRNA-IUR1 deficient mice were generated, and we observed that knockout of murine lncRNA-IUR1 facilitated Bcr-Abl-mediated primary bone marrow transformation. Moreover, animal leukemia model revealed that lncRNA-IUR1 deficiency promoted Abl-transformed cell survival and development of leukemia in mice. Mechanistically, we demonstrated that lncRNA-IUR1 suppressed Bcr-Abl-induced tumorigenesis through negatively regulating STAT5-mediated GATA3 expression. CONCLUSIONS: These findings unveil an inhibitory role of lncRNA-IUR1 in Abl-mediated cellular transformation, and provide new insights into molecular mechanisms underlying Abl-induced leukemogenesis.

The deubiquitinase USP36 Regulates DNA replication stress and confers therapeutic resistance through PrimPol stabilization.

PrimPol has been recently identified as a DNA damage tolerant polymerase that plays an important role in replication stress response. However, the regulatory mechanisms of PrimPol are not well defined. In this study, we identify that the deubiquitinase USP36 interferes with degradation of PrimPol to regulate the replication stress response. Mechanistically, USP36 is deubiquitinated following DNA replication stress, which in turn facilitates its upregulation and interaction with PrimPol. USP36 deubiquitinates K29-linked polyubiquitination of PrimPol and increases its protein stability. Depletion of USP36 results in replication stress-related defects and elevates cell sensitivity to DNA-damage agents, such as cisplatin and olaparib. Moreover, USP36 expression positively correlates with the level of PrimPol protein and poor prognosis in patient samples. These findings indicate that the regulation of PrimPol K29-linked ubiquitination by USP36 plays a critical role in DNA replication stress and chemotherapy response.

Mixed-lineage leukemia protein modulates the loading of let-7a onto AGO1 by recruiting RAN.

Not available.

Long Noncoding RNA Lnc-MxA Inhibits Beta Interferon Transcription by Forming RNA-DNA Triplexes at Its Promoter.

Previously, we identified a set of long noncoding RNAs (lncRNAs) that were differentially expressed in influenza A virus (IAV)-infected cells. In this study, we focused on lnc-MxA, which is upregulated during IAV infection. We found that the overexpression of lnc-MxA facilitates the replication of IAV, while the knockdown of lnc-MxA inhibits viral replication. Further studies demonstrated that lnc-MxA is an interferon-stimulated gene. However, lnc-MxA inhibits the Sendai virus (SeV)- and IAV-induced activation of beta interferon (IFN-ß). A luciferase assay indicated that lnc-MxA inhibits the activation of the IFN-ß reporter upon stimulation with RIG-I, MAVS, TBK1, or active IRF3 (IRF3-5D). These data indicated that lnc-MxA negatively regulates the RIG-I-mediated antiviral immune response. A chromatin immunoprecipitation (ChIP) assay showed that the enrichment of IRF3 and p65 at the IFN-ß promoter in lnc-MxA-overexpressing cells was significantly lower than that in control cells, indicating that lnc-MxA interfered with the binding of IRF3 and p65 to the IFN-ß promoter. Chromatin isolation by RNA purification (ChIRP), triplex pulldown, and biolayer interferometry assays indicated that lnc-MxA can bind to the IFN-ß promoter. Furthermore, an electrophoretic mobility shift assay (EMSA) showed that lnc-MxA can form complexes with the IFN-ß promoter fragment. These results demonstrated that lnc-MxA can form a triplex with the IFN-ß promoter to interfere with the activation of IFN-ß transcription. Using a vesicular stomatitis virus (VSV) infection assay, we confirmed that lnc-MxA can repress the RIG-I-like receptor (RLR)-mediated antiviral immune response and influence the antiviral status of cells. In conclusion, we revealed that lnc-MxA is an interferon-stimulated gene (ISG) that negatively regulates the transcription of IFN-ß by forming an RNA-DNA triplex.IMPORTANCE IAV can be recognized as a nonself molecular pattern by host immune systems and can cause immune responses. However, the intense immune response induced by influenza virus, known as a "cytokine storm," can also cause widespread tissue damage (X. Z. J. Guo and P. G. Thomas, Semin Immunopathol 39:541-550, 2017, https://doi.org/10.1007/s00281-017-0636-y; S. Yokota, Nihon Rinsho 61:1953-1958, 2003; I. A. Clark, Immunol Cell Biol 85:271-273, 2007). Meanwhile, the detailed mechanisms involved in the balancing of immune responses in host cells are not well understood. Our studies reveal that, as an IFN-inducible gene, lnc-MxA functions as a negative regulator of the antiviral immune response. We uncovered the mechanism by which lnc-MxA inhibits the activation of IFN-ß transcription. Our findings demonstrate that, as an ISG, lnc-MxA plays an important role in the negative-feedback loop involved in maintaining immune homeostasis.

Novel lncRNA-IUR suppresses Bcr-Abl-induced tumorigenesis through regulation of STAT5-CD71 pathway.

BACKGROUND: Long noncoding RNAs (lncRNAs), defined as the transcripts longer than 200 nt without protein-coding capacity, have been found to be aberrantly expressed in diverse human diseases including cancer. A reciprocal translocation between chromosome 9 and 22 generates the chimeric Bcr-Abl oncogene, which is associated with several hematological malignancies. However, the functional relevance between aberrantly expressed lncRNAs and Bcr-Abl-mediated leukemia remains obscure. METHODS: LncRNA cDNA microarray was used to identify novel lncRNAs involved in Bcr-Abl-mediated cellular transformation. To study the functional relevance of novel imatinib-upregulated lncRNA (IUR) family in Abl-induced tumorigenesis, Abl-transformed cell survival and xenografted tumor growth in mice was evaluated. Primary bone marrow transformation and in vivo leukemia transplant using lncRNA-IUR knockdown (KD) transgenic mice were further conducted to corroborate the role of lncRNA-IUR in Abl-induced tumorigenesis. Transcriptome RNA-seq, Western blot, RNA pull down and RNA Immunoprecipitation (RIP) were employed to determine the mechanisms by which lncRNA-IUR-5 regulates Bcr-Abl-mediated tumorigenesis. RESULTS: We identified a conserved lncRNA-IUR family as a key negative regulator of Bcr-Abl-induced tumorigenesis. Increased expression of lncRNA-IUR was detected in both human and mouse Abl-transformed cells upon imatinib treatment. In contrast, reduced expression of lncRNA-IUR was observed in the peripheral blood lymphocytes derived from Bcr-Abl-positive acute lymphoblastic leukemia (ALL) patients compared to normal subjects. Knockdown of lncRNA-IUR remarkably promoted Abl-transformed leukemic cell survival and xenografted tumor growth in mice, whereas overexpression of lncRNA-IUR had opposite effects. Also, silencing murine lncRNA-IUR promoted Bcr-Abl-mediated primary bone marrow transformation and Abl-transformed leukemia cell survival in vivo. Besides, knockdown of murine lncRNA-IUR in transgenic mice provided a favorable microenvironment for development of Abl-mediated leukemia. Finally, we demonstrated that lncRNA-IUR-5 suppressed Bcr-Abl-mediated tumorigenesis by negatively regulating STAT5-mediated expression of CD71. CONCLUSIONS: The results suggest that lncRNA-IUR may act as a critical tumor suppressor in Bcr-Abl-mediated tumorigenesis by suppressing the STAT5-CD71 pathway. This study provides new insights into functional involvement of lncRNAs in leukemogenesis.

Robust expression of vault RNAs induced by influenza A virus plays a critical role in suppression of PKR-mediated innate immunity.

Protein kinase R (PKR) is a vital component of host innate immunity against viral infection. However, the mechanism underlying inactivation of PKR by influenza A virus (IAV) remains elusive. Here, we found that vault RNAs (vtRNAs) were greatly induced in A549 cells and mouse lungs after infection with IAV. The viral NS1 protein was shown to be the inducer triggering the upregulation of vtRNAs. Importantly, silencing vtRNA in A549 cells significantly inhibited IAV replication, whereas overexpression of vtRNAs markedly promoted the viral replication. Furthermore, in vivo studies showed that disrupting vtRNA expression in mice significantly decreased IAV replication in infected lungs. The vtRNA knockdown animals exhibited significantly enhanced resistance to IAV infection, as evidenced by attenuated acute lung injury and spleen atrophy and consequently increased survival rates. Interestingly, vtRNAs promoted viral replication through repressing the activation of PKR and the subsequent antiviral interferon response. In addition, increased expression of vtRNAs was required for efficient suppression of PKR by NS1 during IAV infection. Moreover, vtRNAs were also significantly upregulated by infections of several other viruses and involved in the inactivation of PKR signaling by these viruses. These results reveal a novel mechanism by which some viruses circumvent PKR-mediated innate immunity.

African swine fever virus A137R protein inhibits NF-κB activation via suppression of MyD88 signaling in PK15 and 3D4/21 cells in vitro.

African swine fever (ASF) is an infectious disease with high mortality caused by African swine fever virus (ASFV), which poses a great threat to the global swine industry. ASFV has evolved multiple strategies to evade host antiviral innate immunity by perturbing inflammatory responses and interferon production. However, the molecular mechanisms underlying manipulation of inflammatory responses by ASFV proteins are not fully understood. Here, we report that A137R protein of ASFV is a key suppressor of host inflammatory responses. Ectopic expression of ASFV A137R in HEK293T cells significantly inhibited the activation of IL-8 and NF-κB promoters triggered by Sendai virus (SeV), influenza A virus (IAV), or vesicular stomatitis virus (VSV). Accordingly, forced A137R expression caused a significant decrease in the production of several inflammatory cytokines such as IL-8, IL-6 and TNF-α in the cells infected with SeV or IAV. Similar results were obtained from experiments using A137R overexpressing PK15 and 3D4/21 cells infected with SeV or VSV. Furthermore, we observed that A137R impaired the activation of MAPK and NF-κB signaling pathways, as enhanced expression of A137R significantly decreased the phosphorylation of JNK, p38 and p65 respectively upon viral infection (SeV or IAV) and IL-1ß treatment. Mechanistically, we found that A137R interacted with MyD88, and dampened MyD88-mediated activation of MAPK and NF-κB signaling. Together, these findings uncover a critical role of A137R in restraining host inflammatory responses, and improve our understanding of complicated mechanisms whereby ASFV evades innate immunity.

Influenza A Virus-Induced circRNA circMerTK Negatively Regulates Innate Antiviral Responses.

Circular RNAs (circRNAs) are an important subclass of noncoding RNAs implicated in the regulation of multiple biological processes. However, the functional involvement of circRNAs in the pathogenesis of influenza A viruses (IAVs) remains largely unknown. Here, we employed RNA sequencing (RNA-Seq) to examine the differentially expressed circRNAs in mouse lung tissues challenged or not challenged with IAV to evaluate the impact of viral infection on circRNAs in vivo. We observed that 413 circRNAs exhibited significantly altered levels following IAV infection. Among these, circMerTK, the derivative of myeloid-epithelial-reproductive tyrosine kinase (MerTK) pre-mRNA, was highly induced by IAV. Interestingly, circMerTK expression was also increased upon infection with multiple DNA and RNA viruses in human and animal cell lines, and thus it was selected for further studies. Poly(I:C) and interferon ß (IFN-ß) stimulated circMerTK expression, while RIG-I knockout and IFNAR1 knockout cell lines failed to elevate circMerTK levels after IAV infection, demonstrating that circMerTK is regulated by IFN signaling. Furthermore, circMerTK overexpression or silencing accelerated or impeded IAV and Sendai virus replication, respectively. Silencing circMerTK enhanced the production of type I IFNs and interferon-stimulating genes (ISGs), whereas circMerTK overexpression suppressed their expression at both the mRNA and protein levels. Notably, altering circMerTK expression had no effect on the MerTK mRNA level in cells infected or not infected with IAV, and vice versa. In addition, human circMerTK and mouse homologs functioned similarly in antiviral responses. Together, these results identify circMerTK as an enhancer of IAV replication through suppression of antiviral immunity. IMPORTANCE CircRNAs are an important class of noncoding RNAs characterized by a covalently closed circular structure. CircRNAs have been proven to impact numerous cellular processes, where they conduct specialized biological activities. In addition, circRNAs are believed to play a crucial role in regulating immune responses. Nevertheless, the functions of circRNAs in the innate immunity against IAV infection remain obscure. In this study, we employed transcriptomic analysis to investigate the alterations in circRNAs expression following IAV infection in vivo. It was found that expression of 413 circRNAs was significantly altered, of which 171 were upregulated, and 242 were downregulated following the IAV infection. Interestingly, circMerTK was identified as a positive regulator of IAV replication in both human and mouse hosts. CircMerTK was shown to influence IFN-ß production and its downstream signaling, enhancing IAV replication. This finding provides new insights into the critical roles of circRNAs in regulating antiviral immunity.

STAT3 regulates antiviral immunity by suppressing excessive interferon signaling.

This study identifies interleukin-6 (IL-6)-independent phosphorylation of STAT3 Y705 at the early stage of infection with several viruses, including influenza A virus (IAV). Such activation of STAT3 is dependent on the retinoic acid-induced gene I/mitochondrial antiviral-signaling protein/spleen tyrosine kinase (RIG-I/MAVS/Syk) axis and critical for antiviral immunity. We generate STAT3Y705F/+ knockin mice that display a remarkably suppressed antiviral response to IAV infection, as evidenced by impaired expression of several antiviral genes, severe lung tissue injury, and poor survival compared with wild-type animals. Mechanistically, STAT3 Y705 phosphorylation restrains IAV pathogenesis by repressing excessive production of interferons (IFNs). Blocking phosphorylation significantly augments the expression of type I and III IFNs, potentiating the virulence of IAV in mice. Importantly, knockout of IFNAR1 or IFNLR1 in STAT3Y705F/+ mice protects the animals from lung injury and reduces viral load. The results indicate that activation of STAT3 by Y705 phosphorylation is vital for establishment of effective antiviral immunity by suppressing excessive IFN signaling induced by viral infection.

Highly efficient lithium adsorption and stable isotope separation by metal-organic frameworks.

The effects of a series of MOFs on the adsorption and separation of lithium isotopes were investigated in this paper. Seven kinds of MOF were prepared, and the characterization studies of MIL-100(Fe) before and after adsorption by X-ray photoelectron spectroscopy (XPS) demonstrated the potential chemical interaction between Fe and Li. The influence of metal ions, counter-ions and solvents on the adsorption capacity and separation factor was investigated. The maximum separation factor can reach 1.048 ± 0.001. MIL-100(Fe) also has good regeneration performance.

[Effect of eIF4B knockout on apoptosis of mouse fetal liver cells].

Eukaryotic translation initiation factor 4B (eIF4B) plays an important role in mRNA translation initiation, cell survival and proliferation in vitro, but the in vivo function is poorly understood. In this study, via various experimental techniques such as hematoxylin-eosin (HE) staining, flow cytometry, Western blotting, and immunohistochemistry, we investigated the role of eIF4B in mouse embryo development using an eIF4B knockout (KO) mouse model and explored the mechanism. We found that the livers, but not lungs, brain, stomach, or pancreas, derived from eIF4B KO mouse embryos displayed severe pathological changes characterized by enhanced apoptosis and necrosis. Accordingly, high expression of cleaved-caspase 3, and excessive activation of mTOR signaling as evidenced by increased expression and phosphorylation of p70S6K and enhanced phosphorylation of 4EBP1, were observed in mouse embryonic fibroblasts and fetal livers from eIF4B KO mice. These results uncover a critical role of eIF4B in mouse embryo development and provide important insights into the biological functions of eIF4B in vivo.

Initial activation of STAT2 induced by IAV infection is critical for innate antiviral immunity.

STAT2 is an important transcription factor activated by interferons (IFNs) upon viral infection and plays a key role in antiviral responses. Interestingly, here we found that phosphorylation of STAT2 could be induced by several viruses at early infection stage, including influenza A virus (IAV), and such initial activation of STAT2 was independent of type I IFNs and JAK kinases. Furthermore, it was observed that the early activation of STAT2 during viral infection was mainly regulated by the RIG-I/MAVS-dependent pathway. Disruption of STAT2 phosphorylation at Tyr690 restrained antiviral response, as silencing STAT2 or blocking STAT2 Y690 phosphorylation suppressed the expression of several interferon-stimulated genes (ISGs), thereby facilitating viral replication. In vitro experiments using overexpression system or kinase inhibitors showed that several kinases including MAPK12 and Syk were involved in regulation of the early phosphorylation of STAT2 triggered by IAV infection. Moreover, when MAPK12 kinase was inhibited, expression of several ISGs was clearly decreased in cells infected with IAV at the early infection stage. Accordingly, inhibition of MAPK12 accelerated the replication of influenza virus in host. These results provide a better understanding of how initial activation of STAT2 and the early antiviral responses are induced by the viral infection.

I226R Protein of African Swine Fever Virus Is a Suppressor of Innate Antiviral Responses.

African swine fever is one of the most devastating swine diseases caused by African swine fever virus (ASFV). Although ASFV encodes more than 160 viral proteins, the implication of a majority of ASFV proteins in regulating host immunity is yet to be explored, and the mechanisms of immune evasion by ASFV proteins are largely unknown. Here, we report that the I226R protein of ASFV significantly suppressed innate immune responses. The ectopic expression of ASFV I226R in 293T cells significantly inhibited the activation of interferon-stimulated response element promoters triggered by Sendai virus (SeV), poly(I:C), or cyclic GMP-AMP synthase (cGAS)/STING. The I226R protein caused a significant decrease in the expression of interferons and interferon-stimulating genes in cells infected with SeV. Similar results were obtained from experiments using I226R-overexpressed PK15 and 3D4/21 cells stimulated with vesicular stomatitis virus. We observed that I226R inhibited the activation of both nuclear factor-kappa B (NF-κB) and interferon regulatory factor 3 (IRF3). Furthermore, it was shown that overexpression of I226R suppressed IRF3 activation and caused the degradation of NF-κB essential modulator (NEMO) protein. The I226R-induced NEMO degradation could be prevented by treatment with MG132, a proteasome inhibitor. Together, these results reveal that the ASFV I226R protein impairs antiviral responses, likely through multiple mechanisms including the suppression of NF-κB and IRF3 activation, to counteract innate immune responses during the viral infection.

MIR155HG Plays a Bivalent Role in Regulating Innate Antiviral Immunity by Encoding Long Noncoding RNA-155 and microRNA-155-5p.

MIR155HG encodes a precursor RNA of microRNA-155 (miRNA-155). We previously identified this RNA also as a long noncoding RNA (lncRNA) that we call lncRNA-155. To define the functions of miRNA-155 and lncRNA-155, we generated miRNA-155 knockout (KO) mice lacking only 19 bp of the miRNA-155 core sequence without affecting the expression of lncRNA-155. Surprisingly, compared with the miRNA-155KO mice, previously generated lncRNA-155KO mice were more susceptible to both influenza virus (RNA virus) and pseudorabies virus (DNA virus) infection, as characterized by lower survival rate, higher body weight loss, and higher viral load. We found that miRNA-155-5p enhanced antiviral responses by positively regulating activation of signal transducer and activator of transcription 1 (STAT1), but the STAT1 activity differed greatly in the animals (lncRNA-155KO < miRNA-155KO < wild type). In line with this, expression levels of several critical interferon-stimulated genes (ISGs) were also significantly different (lncRNA-155KO < miRNA-155KO < wild type). We found that lncRNA-155 augmented interferon beta (IFN-ß) production during the viral infection, but miRNA-155 had no significant effect on the virus-induced IFN-ß expression. Furthermore, we observed that lncRNA-155 loss in mice resulted in dramatic inhibition of virus-induced activation of interferon regulatory factor 3 compared to both miRNA-155KO and wild-type (WT) animals. Moreover, lncRNA-155 still significantly suppressed the viral infection even though the miRNA-155 derived from lncRNA-155 was deleted or blocked. These results reveal that lncRNA-155 and miRNA-155 regulate antiviral responses through distinct mechanisms, indicating a bivalent role for MIR155HG in innate immunity. IMPORTANCE Here, we found that lncRNA-155KO mice lacking most of the lncRNA-155 sequences along with pre-miRNA-155, were more susceptible to influenza virus or pseudorabies virus infection than miRNA-155KO mice lacking only 19 bp of the miRNA-155 core sequence without affecting the expression of lncRNA-155, as evidenced by faster body weight loss, poorer survival, and higher viral load, suggesting an additional role of lncRNA-155 in regulating viral pathogenesis besides via processing miRNA-155. Congruously, miRNA-155-deleted lncRNA-155 significantly attenuated the viral infection. Mechanistically, we demonstrated miRNA-155-5p potentiated antiviral responses by promoting STAT1 activation but could not directly regulate the IFN-ß expression. In contrast, lncRNA-155 enhanced virus-induced IFN-ß production by regulating the activation of interferon regulatory factor 3. This finding reveals a bivalent role of MIR155HG in regulating antiviral responses through encoding lncRNA-155 and miRNA-155-5p and provides new insights into complicated mechanisms underlying interaction between virus and host innate immunity.